Quantization of continuous parameters or re-quantization of quantized parameters is a common task in digital signal processing, causing a quantization error. In order to reduce the impact of the introduced quantization error, noise shaping is often used in order to minimize the error energy introduced by means of the quantization in a frequency range of interest. To this end, it is determined that the spectrum of a noise-shaped quantized parameter exhibits a noise component or a noise floor which contains a reduced amount of error energy within a frequency range of particular interest. Application scenarios for noise shaping are various.
For example, in a wireless telecommunications application, there may be some points where the word length of a digital signal is reduced. For example, when numerically exact digital signal processing circuits steer analog circuits like, for example, a digital-to-analog converter (DAC), a digitally-controlled oscillator (DCO) or a digital-to-time converter (DTC), quantization of the exact steering values may be required for implementation reasons. Noise shaping and quantization of the steering values results in output data stream of an associated series of noise shaped quantized parameters. Example for steering values are a digital in-phase (I) quadrature (Q), radius (R), phase (Φ) and frequency data. Quantizing those input data streams and shaping the noise according to the requirements results in an output data stream having data words with reduced word length for each of the I, Q, R, Φ and frequency data streams. While noise shaping each of the input data streams independently may result with a satisfactory noise behavior of each of the output data streams. However, when a quantized parameter contributes to the generation of an output signal together with a further quantized parameter the desired spectral properties of the output signal may not be achievable using those conventional noise shaping approaches. In wireless transceivers, for example, a transmitted radio frequency (RF) signal or an associated baseband signal is often generated using two quantities, for example an I- and a Q-component or, an R- and a Φ-component in the polar implementation of the transceiver. While the two components contributing to the generation of the radio frequency or baseband signals may individually exhibit the desirable spectral behavior when noise shaped independently from one another, the resultant RF or baseband output signal may not.
Hence, there may be a desire, to improve noise shaping for quantized parameters contributing to the generation of an output signal.